Php basics

PHP
BASICS
Self learning by
V.S.Hewitt

Introduction
• Can be embedded into webpages and has the syntax similar to C, C++.
Embedding PHP codes in web pages:
It is possible to insert PHP codes directly into Html
pages.
Default Syntax
The default delimiter syntax opens with <?php and
concludes with ?>
Short-Tags:
<?
print "This is another PHP example.";
?>
Short-circuit syntax:
<?="This is another PHP example.";?>
Script:
<script language="php">
print "This is another PHP example.";
</script>
Commenting Your Code
Single-Line C++ Syntax:
// Title: My first PHP script
Shell Syntax:
# Title: My PHP program
Multiple-Line C Syntax: /*………….*/

Outputting Data to the Browser:
A prototype is simply the function’s definition,
formalizing its name, input parameters,and the type of
value it returns, defined by a datatype.
The print() Statement: int print(argument)
<?php
print("<p>I love the summertime.</p>");
?>
<?php
$season = "summertime";
print "<p>I love the $season.</p>";
?>
echo $heavyweight, " and ", $lightweight, " are great fighters.";
Echo can be used to print out multiple arguments.
The printf() Statement:
boolean printf(string format [, mixed args])
It separates the static and dynamic data into two
distinct sections,
printf("Bar inventory: %d bottles of tonic water.", 100);
Type specifiers: %b,%c,%d,%f,%o,%s,%u,%x,%X
The sprintf() Statement:
Similar to printf(), output is assigned to a string.
string sprintf(string format [, mixed arguments])
PHP’s Supported Datatypes:
Boolean, integer(8,10,16), float, string, and array
Object:
class Appliance {
private $_power;
function setPower($status) {
$this->_power = $status;
}}
$blender = new Appliance;
Class definition and object declaration is needed.
Converting Between Datatypes Using Type Casting:
(datatype)variable- convert variable to ‘datatype’
$score = (int) 14.8; // $score = 14
*any datatype can be cast as an object.
print $ obj->scalar; // returns "Toyota"

Adapting Datatypes with Type Juggling:
Variables are sometimes automatically
Cast to best fit the circumstances.
<?php
$total = 5; // an integer
$count = "15"; // a string
$total += $count; // $total = 20 (an integer)
?>
<?php
$total = "45 fire engines";
$incoming = 10;
$total = $incoming + $total; // $total = 55
?>
Type-Related Functions:
string gettype (mixed var)-gives variable type.
boolean settype(mixed var, string type)-converts the variable
to the specified type.
Type Identifier Functions:
is_array(), is_bool(),is_float(), is_integer(), is_null(),
is_numeric(), is_object(), is_resource(), is_scalar(), and
is_string().
Identifiers(case sensitive): (not a keyword)
variables, functions, and various other userdefined
objects.(must begin with a letter or an underscore.)
Variables: can store different values at different times.
Variable Declaration: always begins with a dollar sign $
variables do not have to be explicitly declared in PHP .
Value Assignment:
By value: By reference:
$color = "red"; <?php
$number = 12; $value1 = "Hello";
$age = 12; $value2 =& $value1;//Both “Goodbye”
$sum = 12 + "15"; // $sum = 27 $value2 = "Goodbye"; ?>
Variable Scope:Local variables(declared in a function),
Function parameters(only pass by value), Global
variables(eg. GLOBAL $somevar;), Static variables(STATIC
$somevar;)
Superglobal :$_SERVER,$_GET,$_POST,$_COOKIE,$_FILES,$_ENV

Variable Variables:
$recipe = "spaghetti"; $$recipe = "& meatballs";(value used as variable)
echo $recipe $spaghetti;//spaghetti meatballs
echo $recipe ${$recipe};
Constants:
Cannot be modified, defined by define().
boolean define(string name, mixed value [, bool case_insensitive])
Constants are global.
Expressions: particular action in program contains
atleast one or more operands.
Operands: inputs of an expression.
Operators: symbol specifying an action.
Operator Precedence: the order in which an expression
is evaluated same as elementary maths.
Operator Associativity: how operations of same
precedence are evaluated.
Arithmetic Operators: +,-,*,/,%
Assignment Operators: =,+=,-=,*=,/=,.=(concat. Assign)
Increment and Decrement Operators: ++,--
Logical Operators: &&-AND,||-OR,!-NOT,XOR.
Equality Operators: ==,!=, === (same type)
Comparison Operators: <,>,<=,>=, ?:
Bitwise Operators: &,|,^,~,>>,<<
String Interpolation: double quotes are commonly
used and escape sequence can also be parsed. Single
quotes is used to display the content without any
interpretation of variable and escape sequences.
Escape sequences: n,r,t,,$,”
Heredoc syntax : identical identifiers, start with <<< ,
double quotes need not be escaped. Variables and
escape sequences are parsed. Identifier should be dealt
with space problems.
Control Structures:
Conditional Statements:
The if Statement: checks the given condition.
if ($_POST['guess'] == $secretNumber) echo "<p>Congratulations!</p>";
Single statement of if statement.
The else Statement: when if condition is false
The elseif Statement: either-or situation
The switch Statement: its similar to elseif has an action
for each possible value.

Looping Statements:
The while Statement, The do...while Statement, The for
Statement, The foreach Statement,The break and goto
Statements
File-Inclusion Statements:
The include() Statement: include(/path/to/filename)
for conditional inclusion parenthesis is important.
The include_once() :includes the file if not present otherwise
wont be executed.
The require() and require_once() statements are different to
the include statement to certain extend.

Php basics

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